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 permitted to dispose of wastewater in the soil when certain requirements are met, and rejectOrders when not met. [3] Additionally, the Commission adjudicates certain oil and gasdisputes between owners, including disputes where the state is a party. It is designed tocooperate with industry, while still meeting its regulatory requirements. [4] The Commission'swebsite lists their primary mission is "to protect the public interest in exploration and

development of oil and gas resources, while ensuring conservation practices, enhancingresource recovery, and protecting the health, safety, environment, and property rights of Alaskans."[5] Though the Cook Inletkeeper website notes "2 billion gallons of toxic waste" aredisposed of in the Cook Inlet waterway every year by oil corporations

GasesNatural gas is a gas consisting primarily of methane, typically with 0-20% higher hydrocarbons[1] (primarily ethane). It is found associated with other fossil fuels, in coal beds,as methane clathrates, and is created by methanogenic organisms in marshes, bogs, andlandfills. It is an important fuel source and a major feedstock for fertilizers.

Before natural gas can be used as a fuel, it must undergo processing to remove almost allmaterials other than methane. The by-products of that processing include ethane, propane,

 butanes, pentanes, and higher molecular weight hydrocarbons, elemental sulfur , carbondioxide, water vapor , and sometimes helium and nitrogen.

 Natural gas is often informally referred to as simply gas, especially when compared to other 

energy sources such as oil or coal.

Contents[hide]

• 1 Sources

○ 1.1 Fossil natural gas

○ 1.2 Town gas

○ 1.3 Biogas

○ 1.4 Crystallized natural gas - Hydrates

• 2 Natural gas processing

• 3 Uses

○ 3.1 Power generation

○ 3.2 Domestic use

○ 3.3 Transportation

○ 3.4 Fertilizers

○ 3.5 Aviation

○ 3.6 Hydrogen

○ 3.7 Other

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• 4 Storage and transport

• 5 Environmental effects

○ 5.1 CO2 emissions

○ 5.2 Other pollutants

• 6 Safety

• 7 Energy content, statistics and pricing

○ 7.1 United Kingdom

○ 7.2 European Union

○ 7.3 United States

○ 7.4 Elsewhere

• 8 See also

• 9 References

• 10 External links

[edit] SourcesSee also: List of natural gas fields, List of countries by natural gas proven

reserves, and List of countries by natural gas production

[edit] Fossil natural gas

Natural gas drilling rig in Texas.

In the 1800s, natural gas was usually produced as a byproduct of   producing oil, since the

small, light gas carbon chains come out of solution as it undergoes pressure reduction fromthe reservoir  to the surface, similar to uncapping a bottle of soda pop where the carbon

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dioxide effervesces. Unwanted natural gas can be a disposal problem at the well site. If thereis not a market for natural gas near the wellhead it was virtually valueless since it must be

 piped to the end user. In the 1800s and early 1900s, such unwanted gas was usually burnedoff at the wellsite. Often, unwanted gas (or 'stranded' gas without a market) is pumped back into the reservoir with an 'injection' well for disposal or repressurizing the producing

formation. Today, in locations with a high natural gas demand (such as the United States), pipelines are constructed to take the gas from the wellsite to the end consumer .

Another solution is to export the natural gas as a liquid.[2] Gas-to-liquid (GTL) is adeveloping technology that converts stranded natural gas into synthetic gasoline, diesel or jetfuel through the Fischer-Tropsch  process developed in World War II Germany. Such fuel can

 be transported to users through conventional pipelines and tankers. Proponents claim GTL burn cleaner than comparable petroleum fuels. Most major international oil companies are inan advanced stage of GTL production, with a world-scale (140,000 barrels a day) GTL plantin Qatar scheduled to be in production before 2010.

Fossil natural gas can be "associated" (found in oil fields) or "non-associated" (isolated innatural gas fields), and is also found in coal beds (as coalbed methane). It sometimes containsa significant amount of ethane,  propane, butane, and pentane — heavier hydrocarbonsremoved prior to use as a consumer fuel — as well as carbon dioxide, nitrogen, helium andhydrogen sulfide.[3]

 Natural gas is commercially produced from oil fields and natural gas fields. Gas producedfrom oil wells is called casinghead gas or associated gas. The natural gas industry is

 producing gas from increasingly more challenging resource types: sour gas, tight gas, shalegas and coalbed methane.

The world's largest proven gas reserves are located in Russia, with 4.757 × 1013 m³ (1.6 × 1015

cubic feet). With the Gazprom company, Russia is frequently the world's largest natural gas producer. Major proven resources (in billion cubic meters) are world 175,400 (2006), Russia

47,570 (2006), Iran 26,370 (2006), Qatar 25,790 (2007), Saudi Arabia 6,568 (2006) andUnited Arab Emirates 5,823 (2006). It is estimated that there are also about 900 tetrillion cubic meters of "unconventional" gas such as shale gas, of which 180 tetrillion may berecoverable.[4]

The world's largest gas field is Qatar 's offshore North Field, estimated to have 25 trillioncubic meters[5] (9.0 × 1014cubic feet) of gas in place—enough to last more than 200 years atoptimum production levels. The second largest natural gas field is the South Pars Gas Field inIranian waters in the Persian Gulf . Located next to Qatar's North Field, it has an estimatedreserve of 8 to 14 trillion cubic meters[6] (2.8 × 1014 to 5.0 × 1014 cubic feet) of gas.

Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under supercritical (pressure/temperature) conditions,the higher molecular weight components may partially condense upon isothermicdepressurizing — an effect called retrograde condensation. The liquid thus formed may gettrapped as the pores of the gas reservoir get deposited. One method to deal with this problemis to re-inject dried gas free of condensate to maintain the underground pressure and to allowre-evaporation and extraction of condensates.

[edit] Town gas

Town gas is a synthetically produced mixture of methane and other gases, mainly the highlytoxic carbon monoxide, that can be used in a similar way to natural gas and can be produced

 by treating coal chemically. This is a historic technology, still used as 'best solution' in some

local circumstances, although coal gasification is not usually economic at current gas prices.However, depending upon infrastructure considerations, it remains a future possibility.

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Most town "gashouses" located in the eastern United States in the late nineteenth and earlytwentieth centuries were simple by-product coke ovens which heated bituminous coal in air-tight chambers. The gas driven off from the coal was collected and distributed through town-wide networks of pipes to residences and other buildings where it was used for cooking andlighting purposes. (Gas heating did not come into widespread use until the last half of the

twentieth century.) The coal tar that collected in the bottoms of the gashouse ovens was oftenused for roofing and other water-proofing purposes, and also, when mixed with sand andgravel, was used for creating bitumen for the surfacing of local streets!

[edit] Biogas

When methane-rich gases are produced by the anaerobic decay of non-fossil organic matter ( biomass), these are referred to as biogas (or natural biogas). Sources of biogas includeswamps, marshes, and landfills (see landfill gas), as well as sewage sludge and manure[7]   byway of anaerobic digesters, in addition to enteric fermentation  particularly in cattle.

Methanogenic archaea are responsible for all biological sources of methane, some insymbiotic relationships with other life forms, including termites, ruminants, and cultivated

crops. Methane released directly into the atmosphere would be considered a pollutant.However, methane in the atmosphere is oxidized, producing carbon dioxide and water.Methane in the atmosphere has a half life of seven years, meaning that if a tonne of methanewere emitted today, 500 kilograms would have broken down to carbon dioxide and water after seven years.

U.S. natural gas production, 1900–2005. Source: EIA.

Other sources of methane, the principal component of natural gas, include landfill gas, biogasand methane hydrate. Biogas, and especially landfill gas, are already used in some areas, buttheir use could be greatly expanded. Landfill gas is a type of biogas, but biogas usually refersto gas produced from organic material that has not been mixed with other waste.

Landfill gas is created from the decomposition of waste in landfills. If the gas is not removed,the pressure may get so high that it works its way to the surface, causing damage to thelandfill structure, unpleasant odor, vegetation die-off and an explosion hazard. The gas can bevented to the atmosphere, flared or burned to produce electricity or  heat. Experimentalsystems were being proposed for use in parts Hertfordshire, UK and Lyon in France.

Once water vapor  is removed, about half of landfill gas is methane. Almost all of the rest is

carbon dioxide, but there are also small amounts of  nitrogen, oxygen and hydrogen. There areusually trace amounts of hydrogen sulfide and siloxanes, but their concentration varies

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widely. Landfill gas cannot be distributed through utility natural gas pipelines unless it iscleaned up to less than 3% CO2, and a few parts per million H2S, because CO2 and H2Scorrode the pipelines.[8] It is usually more economical to combust the gas on site or within ashort distance of the landfill using a dedicated pipeline. Water vapor is often removed, even if the gas is combusted on site. If low temperatures condense water out of the gas, siloxanes can

 be lowered as well because they tend to condense out with the water vapor. Other non-methane components may also be removed in order to meet emission standards, to preventfouling of the equipment or for environmental considerations. Co-firing landfill gas withnatural gas improves combustion, which lowers emissions.

Gas generated in sewage treatment  plants is commonly used to generate electricity. For example, the Hyperion sewage plant in Los Angeles burns 8 million cubic feet of gas per dayto generate power [9] New York City utilizes gas to run equipment in the sewage plants, togenerate electricity, and in boilers.[10] Using sewage gas to make electricity is not limited tolarge cities. The city of Bakersfield, California uses cogeneration at its sewer plants. [11]

California has 242 sewage wastewater treatment plants, 74 of which have installed anaerobicdigesters. The total biopower generation from the 74 plants is about 66 MW.[12]

Biogas is usually produced using agricultural waste materials, such as otherwise unusable parts of plants and manure. Biogas can also be produced by separating organic materials fromwaste that otherwise goes to landfills. Such method is more efficient than just capturing thelandfill gas it produces. Using materials that would otherwise generate no income, or evencost money to get rid of, improves the profitability and energy balance of biogas production.

Anaerobic lagoons  produce biogas from manure, while biogas reactors can be used for manure or plant parts. Like landfill gas, biogas is mostly methane and carbon dioxide, withsmall amounts of nitrogen, oxygen and hydrogen. However, with the exception of pesticides,there are usually lower levels of contaminants.

 The McMahon natural gas processing plant in Taylor, British Columbia, Canada.[13]

[edit] Crystallized natural gas - Hydrates

Huge quantities of natural gas (primarily methane) exist in the form of hydrates under sediment on offshore continental shelves and on land in arctic regions that experience

 permafrost such as those in Siberia (hydrates require a combination of high pressure and lowtemperature to form). However, as of 2010[update] no technology has been developed to

 produce natural gas economically from hydrates.

It costs anywhere between once and twice as much to produce usable natural gas fromcrystallized natural gas, using current technology.[14]

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[edit] Natural gas processingMain article: Natural gas processing

The image below is a schematic  block flow diagram of a typical natural gas processing plant.It shows the various unit processes used to convert raw natural gas into sales gas pipelined tothe end user markets.

The block flow diagram also shows how processing of the raw natural gas yields byproductsulfur, byproduct ethane, and natural gas liquids (NGL) propane, butanes and natural gasoline(denoted as pentanes +).[15][16][17][18][19]

Schematic flow diagram of a typical natural gas processing plant.

[edit] Uses

[edit] Power generation

 Natural gas is a major source of  electricity generation through the use of gas turbines andsteam turbines. Most grid peaking power plants and some off-grid engine-generators usenatural gas. Particularly high efficiencies can be achieved through combining gas turbineswith a steam turbine in combined cycle mode. Natural gas burns more cleanly than other fossil fuels, such as oil and coal, and produces less carbon dioxide per unit energy released.

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For an equivalent amount of heat, burning natural gas produces about 30% less carbondioxide than burning petroleum and about 45% less than burning coal.[20] Combined cycle

 power generation using natural gas is thus the cleanest source of power available using fossilfuels, and this technology is widely used wherever gas can be obtained at a reasonable cost.Fuel cell technology may eventually provide cleaner options for converting natural gas into

electricity, but as yet it is not price-competitive.

[edit] Domestic use

 The examples and perspective in this article deal primarily with USA

and do not represent a worldwide view of the subject. Please

improve this article and discuss the issue on the talk page.

 Natural gas is supplied to homes where it is used for such purposes as cooking in natural gas- powered ranges and ovens, natural gas-heated clothes dryers, heating/cooling and centralheating. Home or other building heating may include boilers, furnaces, and water heaters.CNG is used in rural homes without connections to piped-in public utility services, or with

 portable grills. Natural gas is also supplied by independent natural gas suppliers through Natural Gas Choice programs throughout the United States. However, due to CNG being lesseconomical than LPG, LPG (propane) is the dominant source of rural gas.

A Washington, D.C. Metrobus, which runs on natural gas.

[edit] Transportation

Compressed natural gas (methane) is a cleaner alternative to other automobile fuels such as

gasoline (petrol) and diesel. As of 2008 there were 9.6 million natural gas vehiclesworldwide, led by Pakistan (2.0 million), Argentina (1.7 million), Brazil (1.6 million), Iran(1.0 million), and India (650,000).[21][22] The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. Gasoline/petrol vehiclesconverted to run on natural gas suffer because of the low compression ratio of their engines,resulting in a cropping of delivered power while running on natural gas (10%-15%). CNG-specific engines, however, use a higher compression ratio due to this fuel's higher octanenumber of 120–130.[23]

[edit] Fertilizers

 Natural gas is a major feedstock for the production of ammonia, via the Haber process, for 

use in fertilizer production.

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[edit] Aviation

Russian aircraft manufacturer  Tupolev is currently running a development program to produce LNG- and hydrogen-powered aircraft.[24] The program has been running since themid-1970s, and seeks to develop LNG and hydrogen variants of the Tu-204 and Tu-334 

 passenger aircraft, and also the Tu-330 cargo aircraft. It claims that at current market prices,

an LNG-powered aircraft would cost 5,000 roubles (~ $218/ £112) less to operate per ton,roughly equivalent to 60%, with considerable reductions to carbon monoxide, hydrocarbonand nitrogen oxide emissions.

The advantages of liquid methane as a jet engine fuel are that it has more specific energy thanthe standard kerosene mixes do and that its low temperature can help cool the air which theengine compresses for greater volumetric efficiency, in effect replacing an intercooler . Alternatively, it can be used to lower the temperature of the exhaust.

[edit] Hydrogen

 Natural gas can be used to produce hydrogen, with one common method being the hydrogen

reformer . Hydrogen has various applications: it is a primary feedstock for the chemicalindustry, a hydrogenating agent, an important commodity for oil refineries, and a fuel sourcein hydrogen vehicles.

[edit] Other

 Natural gas is also used in the manufacture of fabrics, glass, steel, plastics, paint, and other  products.

[edit] Storage and transport

Polyethylene plastic main being placed in a trench.

Because of its low density, it is not easy to transport or store natural gas. Natural gas pipelines are impractical across oceans. Many existing pipelines in North America are closeto reaching their capacity, prompting some politicians representing northern states to speak of 

 potential shortages. In Europe, the gas pipeline network is already dense in the West[25]. New

 pipelines are planned or under construction in Eastern Europe and between gas fields in

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Russia, Near East and  Northern Africa and Western Europe. See also List of natural gas pipelines.

LNG carriers transport liquefied natural gas (LNG) across oceans, while tank trucks can carryliquefied or compressed natural gas (CNG) over shorter distances. Sea transport using CNGcarrier  ships that are now under development may be competitive with LNG transport in

specific conditions.

Gas is turned into liquid at a liquefaction  plant, and is returned to gas form at regasification plant at the terminal. Shipborne regasification equipment is also used. LNG is the preferredform for long distance, high volume transportation of natural gas, whereas pipeline is

 preferred for transport for distances up to 4,000 km over land and approximately half thatdistance offshore.

CNG is transported at high pressure, typically above 200 bars. Compressors anddecompression equipment are less capital intensive and may be economical in smaller unitsizes than liquefaction/regasification plants. Natural gas trucks and carriers may transportnatural gas directly to end-users, or to distribution points such as pipelines.

Peoples Gas Manlove Field natural gas storage area in Newcomb Township,

Champaign County, Illinois. In the foreground (left) is one of the numerous wells

for the underground storage area, with an LNG plant, and above ground storage

tanks is in the background (right).

In the past, the natural gas which was recovered in the course of recovering petroleum couldnot be profitably sold, and was simply burned at the oil field in a process known as flaring. Flaring is now illegal in many countries.[26] Additionally, companies now recognize that gasmay be sold to consumers in the form of LNG or CNG, or through other transportation

methods. The gas is now re-injected into the formation for later recovery. The re-injectionalso assists oil pumping by keeping underground pressures higher.

A "master gas system" was invented in Saudi Arabia in the late 1970s, ending any necessityfor flaring. Satellite observation, however, shows that flaring[27] and venting[28] are still

 practiced in some gas-producing countries.

 Natural gas is used to generate electricity and heat for desalination. Similarly, some landfillsthat also discharge methane gases have been set up to capture the methane and generateelectricity.

 Natural gas is often stored underground inside depleted gas reservoirs from previous gaswells, salt domes, or in tanks as liquefied natural gas. The gas is injected in a time of low

demand and extracted when demand picks up. Storage nearby end users helps to meet volatiledemands, but such storage may not always be practicable.

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With 15 countries accounting for 84% of the worldwide production, access to natural gas has become an important issue in international politics, and countries vie for control of pipelines.[29] In the 2000s, Gazprom, the state-owned energy company in Russia, engaged in disputeswith Ukraine and Belarus over the price of natural gas, which have created worries that gasdeliveries to parts of Europe could be cut off for political reasons. [30]

[edit] Environmental effectsSee also: Environmental issues with energy

[edit] CO2 emissions

 Natural gas is often described as the cleanest fossil fuel, producing less carbon dioxide per  joule delivered than either coal or oil[20] and far fewer pollutants than other fossil fuels.However, in absolute terms, it does contribute substantially to global carbon emissions, andthis contribution is projected to grow. According to the IPCC Fourth Assessment Report(Working Group III Report, chapter 4), in 2004, natural gas produced about 5.3 billion tons ayear of CO2 emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively

(figure 4.4). According to an updated version of the SRES B2 emissions scenario, however, by the year 2030, natural gas would be the source of 11 billion tons a year, with coal and oilnow 8.4 and 17.2 billion respectively because demand is increasing 1.9% a year [31] (Totalglobal emissions for 2004 were estimated at over 27,200 million tons).

In addition, natural gas itself is a greenhouse gas more potent than carbon dioxide whenreleased into the atmosphere, although natural gas is released in much smaller quantities.However, methane is oxidized in the atmosphere, and hence natural gas has a residencelifetime in the atmosphere for approximately 12 years, compared to CO2, which is alreadyoxidized, and has an effect for 100 to 500 years. Natural gas is mainly composed of methane,which has a radiative forcing twenty times greater than carbon dioxide. Based on suchcomposition, a ton of methane in the atmosphere traps in as much radiation as 20 tons of carbon dioxide, but remains in the atmosphere for a 8-40 times shorter time. Carbon dioxidestill receives the lion's share of attention over greenhouse gases because it is released in muchlarger amounts. Still, it is inevitable when natural gas is used on a large scale that some of itwill leak into the atmosphere. (However, coal methane is already simply lost into theatmosphere, most methane in the atmosphere is currently from animals and bacteria, not fromman's leaks.). Current estimates by the EPA place global emissions of methane at 3 trillioncubic feet annually,[32] or 3.2% of global production.[33] Direct emissions of methanerepresented 14.3% of all global anthropogenic greenhouse gas emissions in 2004.[34]

[edit] Other pollutants

 Natural gas produces far lower amounts of  sulfur dioxide and nitrous oxides than any other fossil fuel. Carbon dioxide produced is 117,000 ppm vs 208,000 for burning coal. Carbonmonoxide produced is 40 ppm vs 208 for burning coal. Nitrogen oxides produced is 92 ppmvs 457 for burning coal. Sulfur dioxide is 1 ppm vs 2,591 for burning coal. Particulates are 7

 ppm vs 2,744 for burning coal. Mercury is 0 vs .016 for burning coal.[35] Particulates are alsoa major contribution to global warming. Natural gas has 7ppm vs coals 2,744ppm.[36]

[edit] Safety

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A pipeline odorant injection station.

In any form, a minute amount of odorant such as t-butyl mercaptan, with a rotting-cabbage-like smell, is added to the otherwise colorless and almost odorless gas, so that leaks can bedetected before a fire or  explosion occurs. Sometimes a related compound, thiophane is used,with a rotten-egg smell. Adding odorant to natural gas began in the United States after the1937 New London School explosion. The buildup of gas in the school went unnoticed, killingthree hundred students and faculty when it ignited. Odorants are considered non-toxic in theextremely low concentrations occurring in natural gas delivered to the end user.

In mines, where methane seeping from rock formations has no odor, sensors are used, andmining apparatuses have been specifically developed to avoid ignition sources such as theDavy lamp.

Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and boats are most frequently affected when an internal leak builds up gas insidethe structure. Frequently, the blast will be enough to significantly damage a building butleave it standing. In these cases, the people inside tend to have minor to moderate injuries.Occasionally, the gas can collect in high enough quantities to cause a deadly explosion,disintegrating one or more buildings in the process. The gas usually dissipates readilyoutdoors, but can sometimes collect in dangerous quantities if weather conditions are right.However, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low.

Some gas fields yield sour gas containing hydrogen sulfide (H2S). This untreated gas is toxic.Amine gas treating, an industrial scale process which removes acidic gaseous components, is

often used to remove hydrogen sulfide from natural gas.[37]

Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir . Such decreasein pressure in turn may result in subsidence at ground level. Subsidence may affectecosystems, waterways, sewer and water supply systems, foundations, and so on.

 Natural gas heating systems are a minor source of carbon monoxide deaths in the UnitedStates. According to the US Consumer Product Safety Commission (2008), 56% of unintentional deaths from non-fire CO poisoning were associated with engine-driven toolslike gas-powered generators and lawn mowers. Natural gas heating systems accounted for 4%of these deaths. Improvements in natural gas furnace designs have greatly reduced CO

 poisoning concerns. Detectors are also available that warn of carbon monoxide and/or explosive gas (methane, propane, etc.).

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Releasing the gas is accomplished by a environmentally questionable process calledhydrofracking. To force the natural gas out of the shale, drillers force one to nine milliongallons of fresh water through the driven pipe into the shale. The high pressure water breaksup or "fracks" the shale that, in turn, releases the trapped gas. Sand is added to the water as a

 propellant to keep the fractures in the shale open and to enable the gas to flow up the pipe to

the surface. A variety of chemicals are also added to the fresh water to keep the well pipeclean and the gas flowing easily. These chemicals include lubricants to reduce friction, biocides to eliminate fouling, scale inhibitors, oxygen scavengers to reduce oxygen in the borehole, and acids to clean the perforations in the pipe.

Dealing with fracking fluid can be a challenge. Along with the gas, 30% to 70% of thechemically-laced frack fluid, or flow back, rises to the surface. Additionally, a significantamount of salt and other minerals, once a part of the rock layers that were under prehistoricseas, are added to the mix as they dissolve in the frack fluid.

[edit] Energy content, statistics and pricing

Natural gas prices at the Henry Hub in US dollars per million BTUs ($/mmbtu) for

2000-2010.

Main article: Natural gas prices

Quantities of natural gas are measured in normal cubic meters (corresponding to 0°C at101.325 kPa) or in standard cubic feet (corresponding to 60 °F (16 °C) and 14.73  psia). Thegross heat of combustion of one cubic meter of commercial quality natural gas is around39 megajoules (≈10.8 kWh), but this can vary by several percent. This comes to about49 megajoules (≈13.5 kWh) for one kg of natural gas (assuming 0.8 kg/m^3, an approximatevalue).

The price of natural gas varies greatly depending on location and type of consumer. In 2007,a price of $7 per 1,000 cubic feet (28 m3) was typical in the United States. The typical caloricvalue of natural gas is roughly 1,000 British thermal units (BTU) per cubic foot, dependingon gas composition. This corresponds to around $7 per million BTU, or around $7 per gigajoule. In April 2008, the wholesale price was $10 per 1,000 cubic feet (28 m3)($10/MMBTU).[38] The residential price varies from 50% to 300% more than the wholesale

 price. At the end of 2007, this was $12–$16 per 1,000 cu ft (28 m3).[39] Natural gas in theUnited States is traded as a futures contract on the New York Mercantile Exchange. Eachcontract is for 10,000 MMBTU (~10,550 gigajoules), or 10 billion BTU. Thus, if the price of 

gas is $10 per million BTUs on the NYMEX, the contract is worth $100,000.

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[edit] United Kingdom

 Natural gas is also traded as a commodity in Europe, principally at the United Kingdom  NBP and related European hubs, such as the TTF in the Netherlands.

[edit] European Union

As one of the world's largest importers of natural gas, the EU is a major player on theinternational gas market. With Norway being one of the world's largest suppliers of naturalgas as part of the extended European Economic Area, most discussions can be conductedwithin the EU. The main supplier is then expected to be the current number two: the RussianFederation.

Gas prices for end users vary greatly across the EU.[40]. A single European energy market, oneof the key objectives of the European Union, should level the prices of gas in all EU member states.

[edit] United States

In US units, one standard cubic foot of natural gas produces around 1,028 British thermalunits (BTU). The actual heating value when the water formed does not condense is the netheat of combustion and can be as much as 10% less.[41]

In the United States, retail sales are often in units of therms (th); 1 therm = 100,000 BTU.Gas meters measure the volume of gas used, and this is converted to therms by multiplyingthe volume by the energy content of the gas used during that period, which varies slightlyover time. Wholesale transactions are generally done in decatherms (Dth), or in thousanddecatherms (MDth), or in million decatherms (MMDth). A million decatherms is roughly a

 billion cubic feet of natural gas.

As of 2009, the Potential Gas Committee estimated that the United States has total futurerecoverable natural gas resources approximately 100 times greater than current annualconsumption.[42]

[edit] Elsewhere

In the rest of the world, LNG (liquified natural gas) and LPG (liquified petroleum gas) istraded in metric tons or mmBTU as spot deliveries. Long term contracts are signed in metrictons. The LNG and LPG is transported by specialized transport ships, as the gas is liquified atcryogenic temperatures. The specification of each LNG/LPG cargo will usually contain theenergy content, but this information is in general not available to the public.

This article is about the fuel and industrial solvent. For other uses, see Gasoline(disambiguation).

"Petrol" redirects here. For other uses, see  Petrol (disambiguation). The seabird and things named after it are spelled  petrel  ,

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A jar of gasoline

Gasoline or petrol is a petroleum-derived liquid mixture which is primarily used as a fuel ininternal combustion engines. It is also used as a solvent, mainly known for its ability to dilute

 paints.

It consists mostly of aliphatic hydrocarbons obtained by the fractional distillation of  petroleum, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene toincrease its octane rating. Small quantities of various additives are common, for purposessuch as tuning engine performance or reducing harmful exhaust emissions. Some mixtures

also contain significant quantities of ethanol as a partial alternative fuel.Most current or former Commonwealth countries use the term petrol , abbreviated frompetroleum spirit. In North America, the substance is called gasoline, a term often shortenedin colloquial usage to gas. It is not a genuinely gaseous fuel (unlike, for example, liquefied

 petroleum gas, which is stored under pressure as a liquid, but returned to a gaseous state before combustion). The term petrogasoline is also used.[citation needed ]

The term mogas, short for motor gasoline, is used[citation needed ] to distinguish automobile fuelfrom aviation gasoline, or avgas. In British English, gasoline can refer to a different

 petroleum derivative historically used in lamps, but this usage is relatively uncommon.[citation

needed ]

Contents[hide]

• 1 Early uses

• 2 Etymology

• 3 Chemical analysis and production

○ 3.1 Density

○ 3.2 Volatility

○ 3.3 Octane rating

○ 3.4 World War II and octane ratings

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• 4 Energy content (High and low heating value)

• 5 Additives

○ 5.1 Lead

○ 5.2 MMT

○ 5.3 Ethanol

5.3.1 United States

5.3.1.1 European Union

5.3.1.2 Brazil

5.3.1.3 Australia

○ 5.4 Dye

○ 5.5 Oxygenate blending

○ 5.6 Other additives

• 6 Health concerns

• 7 Usage and pricing

○ 7.1 United States

• 8 Stability

• 9 Other fuels

• 10 See also

• 11 Notes

• 12 References

• 13 External links

[edit] Early uses

This section does not cite any references or sources.Please help improve this article  by adding citations to reliable sources. Unsourced material may bechallenged and removed. (April 2009)

Gasoline pumps, Norway

In the United States, gasoline was also sold as a cleaning fluid to remove grease stains fromclothing.[citation needed ] Before dedicated filling stations were established, early motorists boughtgasoline in cans to fill their tanks.

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Gasoline was also used in kitchen ranges and for lighting, and is still available in a purifiedform, known as camping fuel, white gas or Coleman fuel, for use in lanterns and portablestoves.

During the Franco-Prussian War  (1870–71), pétrole was stockpiled in Paris for use against a possible German-Prussian attack on the city.[citation needed ] Later in 1871, during the

revolutionary Paris Commune, rumours spread around the city of  pétroleuses (women using bottles of petrol to commit arson against city buildings).[citation needed ]

[edit] Etymology

A gasoline can (which are typically red) from Midwest Can Company.

The name gasoline is similar to that of other petroleum products of the day, most notably petroleum jelly, a highly purified heavy distillate, which was branded Vaseline. Thetrademark Gasoline was never registered, and eventually became generic in North Americaand the Philippines.

The word "petrol" was first used in reference to the refined substance in 1892 (it was previously used to refer to unrefined petroleum), and was registered as a trade name byBritish wholesaler Carless, Capel & Leonard at the suggestion of Frederick Richard Simms.[1]

Carless's competitors used the term "motor spirit" until the 1930s.[2][3]

In many countries gasoline is called Benzine or some variant. This name for gasoline derivesfrom the chemical benzene. In other countries (Argentina, Uruguay and Paraguay, for example) it's called nafta or some variant.[4]

[edit] Chemical analysis and production

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Oil refineries produce gasoline.

Refinery Minatitlán, Mexico.

A United States pumpjack .

An oil rig in the Gulf of Mexico.

Gasoline is produced in oil refineries. Material that is separated from crude oil via distillation, called virgin or straight-run gasoline, does not meet the required specifications for modernengines (in particular octane rating; see below), but will form part of the blend.

The bulk of a typical gasoline consists of hydrocarbons with between 4 and 12 carbon atoms per  molecule(Commonly referred to as C4-C12).[5]

Many of the hydrocarbons are considered hazardous substances and are regulated in theUnited States by the Occupational Safety and Health Administration. The material safety data

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sheet for unleaded gasoline shows at least fifteen hazardous chemicals occurring in variousamounts, including benzene (up to 5% by volume), toluene (up to 35% by volume),naphthalene (up to 1% by volume), trimethylbenzene (up to 7% by volume), Methyl tert -

 butyl ether (MTBE) (up to 18% by volume, in some states) and about ten others .[6]

The various refinery streams blended together to make gasoline all have different

characteristics. Some important streams are:

• reformate, produced in a catalytic reformer  with a high octane rating and higharomatic content, and very low olefins (alkenes).

• cat cracked gasoline or cat cracked naphtha, produced from a catalytic cracker , with a moderate octane rating, high olefins (alkene) content, and moderate aromaticslevel.

• hydrocrackate (heavy, mid, and light) produced from a hydrocracker, with mediumto low octane rating and moderate aromatic levels.

• virgin or straight-run naphtha, directly from crude oil with low octane rating, lowaromatics (depending on the grade of crude oil), some naphthenes (cycloalkanes) andno olefins (alkenes).

• alkylate, produced in an alkylation unit, with a high octane rating and which is pure paraffin (alkane), mainly branched chains.

• isomerate (various names), which is obtained by isomerizing the pentane andhexane[citation needed ] in light virgin naphthas to yield their higher octane isomers.

The terms above are the jargons used in the oil industry. The exact terminology for thesestreams varies by refinery and by country.

Overall, a typical gasoline is predominantly a mixture of paraffins (alkanes), naphthenes(cycloalkanes), and olefins (alkenes). The actual ratio depend on:

• the oil refinery that makes the gasoline, as not all refineries have the same set of  processing units;

• crude oil feed used by the refinery;

• the grade of gasoline, in particular, the octane rating.

Currently, many countries set limits on gasoline aromatics in general,  benzene in particular,and olefin (alkene) content. Such regulations led to increasing preference for high octane pure

 paraffin (alkane) components, such as alkylate, and is forcing refineries to add processingunits to reduce benzene content.

Gasoline can also contain other  organic compounds such as organic ethers (deliberatelyadded), plus small levels of contaminants, in particular sulfur compounds such as disulfides and thiophenes. Some contaminants, in particular thiols and hydrogen sulfide, must beremoved because they cause corrosion in engines. Sulfur compounds are usually removed byhydrotreating, yielding hydrogen sulfide, which can then be transformed into elemental sulfur via the Claus process.

[edit] Density

The specific density of gasoline ranges from 0.71–0.77, higher densities having a greater volume of aromatics.[7] (0.026 lb/in3 ; 719.7 kg/m3 ; 6.073 lb/US gal; 7.29 lb/imp gal). Gasolinefloats on water; water cannot generally be used to extinguish a gasoline fire, unless used in afine mist.

[edit] Volatility

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A plastic container for storing gasoline used in Germany.

Gasoline is more volatile than diesel oil, Jet-A or  kerosene, not only because of the baseconstituents, but because of the additives that are put into it. The final control of  volatility is

often achieved by blending with  butane. The Reid vapor pressure (RVP) test is used tomeasure the volatility of gasoline. The desired volatility depends on the ambient temperature.In hot weather, gasoline components of higher molecular weight and thus lower volatility areused. In cold weather, too little volatility results in cars failing to start.

In hot weather, excessive volatility results in what is known as "vapor lock ", wherecombustion fails to occur, because the liquid fuel has changed to a gaseous fuel in the fuellines, rendering the fuel pump ineffective and starving the engine of fuel. This effect mainlyapplies to camshaft-driven (engine mounted) fuel pumps which lack a fuel return line.Vehicles with fuel injection require the fuel to be pressurized, to within a set range. Becausecamshaft speed is nearly zero before the engine is started, an electric pump is used. It islocated in the fuel tank so that the fuel may also cool the high-pressure pump. Pressure

regulation is achieved by returning unused fuel to the tank. Therefore, vapor lock is almostnever a problem in a vehicle with fuel injection.

In the United States, volatility is regulated in large cities to reduce the emission of unburnedhydrocarbons. In large cities, so-called reformulated gasoline that is less prone toevaporation, among other properties, is required. In Australia, summer petrol volatility limitsare set by state governments and vary among states. Most countries simply have a summer,winter, and perhaps intermediate limit.

Volatility standards may be relaxed (allowing more gasoline components into theatmosphere) during gasoline shortages. For example, on 31 August 2005, in response toHurricane Katrina, the United States permitted the sale of non-reformulated gasoline in some

urban areas, effectively permitting an early switch from summer to winter-grade gasoline. Asmandated by EPA administrator  Stephen L. Johnson, this "fuel waiver" was made effectiveuntil 15 September 2005.[8]

Other means of controlling emission of unburned hydrocarbons are also used. All vehicleswhich were sold in the United States since in the 1980s, and probably the 1970s or earlier arerequired to have a fuel evaporative control system (called an EVAP system in automotive

 jargon), which collects expanding fuel vapor from the fuel tank in a charcoal-lined canister while the engine is stopped and then releases the collected vapors (through a "purge valve")into the engine intake for burning when the engine is running (usually only after it hasreached normal operating temperature.) The fuel evaporative control system is also requiredto include a gasket filling cap which seals the fueling inlet to prevent vapors from escaping

directly from the tank through it. Modern vehicles with OBD-II emissions control systemswill turn on the malfunction indicator light, or "check engine" light, if it is detected that the

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gas cap is missing or loose, and not sealing. This light indicates whether any of the emissionscontrols are not working properly.

[edit] Octane rating

For more details on this topic, see octane rating.

Internal combustion engines are designed to burn gasoline in a controlled process calleddeflagration. But in some cases, gasoline can also combust abnormally by detonation, whichwastes energy and can damage the engine. One way to reduce detonation is to increase theoctane content of the gasoline, which is expressed by its octane rating.

Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer  of octane) and n-heptane. There are different conventions for expressing octane ratings so a fuelmay have several different octane ratings based on the measure used.

The octane rating became important as the military sought higher output for aircraft engines in the late 1930s and the 1940s, with higher rating indicating higher compression ratio.

[edit] World War II and octane ratings

This article needs additional citations for verification.Please help improve this article  by adding reliable references. Unsourced material may be challengedand removed. (May 2007)

During World War II, Germany received much of its oil from Romania. From 2.8 million barrels (450×10^3 m3) in 1938, Romania’s exports to Germany increased to 13 million barrels(2.1×10^6 m3) by 1941, a level that was essentially maintained through 1942 and 1943, beforedropping by half, due to Allied bombing and mining of the Danube. Although these exportswere almost half of Romania’s total production, they were considerably less than what theGermans expected. Even with the addition of the Romanian deliveries, oil imports over landafter 1939 could not make up for the loss of overseas shipments. To become less dependent

on outside sources, the Germans undertook a sizable expansion program of their own meager domestic oil pumping. After 1938, they had access to the Austrian oil fields, and theexpansion of Nazi crude oil output was chiefly concentrated there. Primarily as a result of thisexpansion, the Reich's domestic output of crude oil increased from approximately 3.8 million

 barrels (600×10^3 m3) in 1938 to almost 12 million barrels (1.9×10^6 m3) in 1944, but eventhat output was not sufficient to meet all the needs of the Nazi military.

Instead, Germany had developed a synthetic fuel capacity that was intended to replaceimported or captured oil. Fuel was generated from coal, using either the Bergius process or the Fischer-Tropsch process. Between 1938 and 1943, synthetic fuel output underwent arespectable growth from 10 to 36 million barrels (1.6–5.7×106 m3). The percentage of synthetic fuels compared with the yield from all sources grew from 22% to more than 50% by

1943. The total oil supplies available from all sources for the same period rose from45 million barrels (7.2×10^6 m3) in 1938 to 71 million barrels (11.3×10^6 m3) in 1943.

By the early 1930s, automobile gasoline had an octane rating of 40 and aviation gasoline arating of 75-80. Aviation gasoline with such high octane numbers could only be refinedthrough a process of distillation of high-grade petroleum. Germany’s domestic oil was not of this quality. Only the additive tetra-ethyl lead could raise the octane to a maximum of 87. Thelicense for the production of this additive was acquired in 1935 from the American holder of the patents, but without high-grade Romanian oil even this additive was not very effective.100 octane fuel, designated either 'C-2' (natural) or 'C-3' (synthethic) was introduced in late1939 with the Daimler-Benz DB 601 N engine, used in certain of the Luftwaffe`s Bf 109E andBf 109F single-engined fighters, Bf 110C twin-engined fighters, and several bomber types.

Some later combat types, most notably the BMW 801D-powered Fw 190A, F and G series, 

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and later war Bf 109G and K models, used C-3 as well. The nominally 87 octane aviationfuel designated 'B-4' was produced in parallel during the war.

In the United States the oil was not "as good", and the oil industry had to invest heavily invarious expensive boosting systems. This turned out to have benefits: the US industry starteddelivering fuels of increasing octane ratings by adding more of the boosting agents, and the

infrastructure was in place for a post-war octane-agents additive industry. Good crude oil wasno longer a factor during wartime, and by war's end American aviation fuel was commonly130 octane, and 150 octane was available in limited quantities for fighters from mid-1944.This high octane could easily be used in existing engines to deliver much more power byincreasing the pressure delivered by the superchargers.

In late 1942, the Germans increased the octane rating of their high-grade 'C-3' aviation fuel to150 octane. The relative volumes of production of the two grades B-4 and C-3 cannot beaccurately given, but in the last war years perhaps two-thirds of the total was C-3. Everyeffort was being made toward the end of the war to increase isoparaffin production; moreisoparaffin meant more C-3 available for fighter plane use.

A common misconception exists concerning wartime fuel octane numbers. There are twooctane numbers for each fuel, one for lean mix and one for rich mix, rich being greater. Themisunderstanding that German fuels had a lower octane number (and thus a poorer quality)arose because the Germans quoted the lean mix octane number for their fuels while the Alliesquoted the rich mix number. Standard German high-grade 'C-3' aviation fuel used in the later 

 part of the war had lean/rich octane numbers of 100/130. The Germans listed this as a 100octane fuel, the Allies as 130 octane.

After the war, the US Navy sent a technical mission to Germany to interview German petrochemists and examine German fuel quality. Its report entitled “Technical Report 145-45Manufacture of Aviation Gasoline in Germany” chemically analyzed the different fuels, andconcluded that “Toward the end of the war the quality of fuel being used by the German

fighter planes was quite similar to that being used by the Allies.”

[edit] Energy content (High and low heating value)

A plastic container used widely for storing gasoline.

Gasoline contains about 35 MJ/L (9.7 kW·h/L, 132 MJ/US gal, 36.6 kWh/US gal) (higher heating value) or 13 kWh/kg. This is an average; gasoline blends differ, and therefore actualenergy content varies from season to season and from batch to batch, by up to 4% more or less than the average, according to the US EPA. On average, about 19.5 US gallons (16.2 impgal; 74 L) of gasoline are available from a 42-US-gallon (35 imp gal; 160 L) barrel of crudeoil (about 46% by volume), varying due to quality of crude and grade of gasoline. The

remaining residue comes off as products ranging from tar to naptha.[9]

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Volumetric and mass energy density of some fuels compared with gasoline (in the rows withgross and net, they are from [10]):

Fuel type[clarification

needed ]

Gross MJ/L MJ/kgGross

BTU/gal

(imp)

GrossBTU/gal

(U.S.)

NetBTU/gal

(U.S.)

  RON

Conventionalgasoline

34.8 44.4[11] 150,100 125,000 115,400

Autogas (LPG)(60% Propane +40% Butane)[citation

needed ]

26.8 46 108

Ethanol 21.2[11] 26.8[11] 101,600 84,600 75,700 113[12]

Methanol 17.9 19.9[11] 77,600 64,600 56,600 123

Butanol[2]  29.2 36.691-99[clarification

needed ]

Gasohol 31.2 145,200 120,900 112,40093/94[clarification

needed ]

Diesel(*) 38.6 45.4 166,600 138,700 128,700 25

Biodiesel33.3-35.7 [13]

[clarification needed ] 126,200 117,100

Aviation gasoline (high octanegasoline, not jetfuel)

33.5 46.8 144,400 120,200 112,000

Jet fuel (kerosene

 based)

35.1 43.8 151,242 125,935

Jet fuel (naphtha) 127,500 118,700

Liquefied naturalgas

25.3 ~55 109,000 90,800

Liquefied petroleum gas

91,300 83,500

Hydrogen10.1 (at 20

kelvins)142 130[14]

(*) Diesel fuel is not used in a gasoline engine, so its low octane rating is not an issue; the relevant metric for diesel engines is the cetane number 

A high octane fuel such as liquefied petroleum gas (LPG) has a lower energy content thanlower octane gasoline, resulting in an overall lower power output at the regular compressionratio an engine ran at on gasoline. However, with an engine tuned to the use of LPG (i.e. viahigher compression ratios such as 12:1 instead of 8:1), this lower power output can beovercome. This is because higher-octane fuels allow for a higher  compression ratio —thismeans less space in a cylinder on its combustion stroke, hence a higher cylinder temperaturewhich improves efficiency according to Carnot's theorem, along with fewer wastedhydrocarbons (therefore less pollution and wasted energy), bringing higher power levelscoupled with less pollution overall because of the greater combustion efficiency. Also,increased mechanical efficiency is created by a higher compression ratio through theconcommitant higher expansion ratio on the power stroke, which is by far the greater affect.The higher expansion ratio extracts more work from the high pressure gas created by thecombustion process. The applicable formula is PV=nRT. An Atkinson cycle engine uses thetiming of the valve events to produce the benefits of a high expansion ratio without the

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disadvantages, chiefly detonation, of a high compression ratio. A high expansion ratio is alsoone of the two key reasons for the efficiency of Diesel engines, along with the elimination of 

 pumping losses due to throtttling of the intake air flow. A high compression ratio can beviewed as a necessary evil in order to have a high expansion ratio.

The main reason for the lower energy content (per litre) of LPG in comparison to gasoline is

that it has a lower density. Energy content per kilogram is higher than for gasoline (higher hydrogen to carbon ratio). The weight-density of gasoline is about 740 kg/m³(6.175 lb/US gal; 7.416 lb/imp gal).

Different countries have some variation in what RON (research octane number) is standardfor gasoline, or petrol. In the UK, ordinary regular unleaded petrol is 91 RON (not commonlyavailable), premium unleaded petrol is always 95 RON, and super unleaded is usually 97-98RON. However both Shell and BP produce fuel at 102 RON for cars with hi-performanceengines, and the supermarket chain Tesco began in 2006 to sell super unleaded petrol rated at99 RON. In the US, octane ratings in unleaded fuels can vary between 86-87 AKI (91-92RON) for regular, through 89-90 AKI (94-95 RON) for mid-grade (European Premium), upto 90-94 AKI (95-99 RON) for premium (European Super).

[edit] AdditivesMain article: Gasoline additive

[edit] Lead

The mixture known as gasoline, when used in high compression internal combustion engines,has a tendency to autoignite (detonation) causing a damaging "engine knocking" (also called"pinging" or "pinking") noise. Early research into this effect was led by A.H. Gibson andHarry Ricardo in England and Thomas Midgley and Thomas Boyd in the United States. Thediscovery that lead additives modified this behavior led to the widespread adoption of their use in the 1920s and therefore more powerful higher compression engines. The most popular 

additive was tetra-ethyl lead. Its use continued for decades despite the deaths of severalmembers of the original research teams from lead poisoning. Marketing materials purposelyavoided mentioning lead explicitly, and instead "Ethyl" was used. However, with thediscovery of the extent of environmental and health damage caused by the lead, and theincompatibility of lead with catalytic converters found on virtually all newly sold USautomobiles since 1975, this practice began to wane (encouraged by many governmentsintroducing differential tax rates) in the 1980s. Most countries are phasing out leaded fuel;different additives have replaced the lead compounds. The most popular additives includearomatic hydrocarbons, ethers and alcohol (usually ethanol or  methanol). In the US, wherelead had been blended with gasoline (primarily to boost octane levels) since the early 1920s,standards to phase out leaded gasoline were first implemented in 1973 - due in great part to

studies conducted by Philip J. Landrigan. In 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2000 short tons (1814 t) of lead per year. From 1 January1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possessionand use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 finein the US. However, fuel containing lead may continue to be sold for off-road uses, includingaircraft, racing cars, farm equipment, and marine engines.[15] Similar bans in other countrieshave resulted in lowering levels of lead in people's bloodstreams.[16][17]

A side effect of the lead additives was protection of the valve seats from erosion. Manyclassic cars' engines have needed modification to use lead-free fuels since leaded fuels

 became unavailable. However, "Lead substitute" products are also produced and cansometimes be found at auto parts stores. These were scientifically tested and some wereapproved by the Federation of British Historic Vehicle Clubs at the UK's Motor IndustryResearch Association (MIRA) in 1999.[18]

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In some parts of South America, Asia, Eastern Europe and the Middle East, leaded gasoline isstill in use. Leaded gasoline was phased out in sub-Saharan Africa effective 1 January 2006.A growing number of countries have drawn up plans to ban leaded gasoline in the near future.

[edit] MMT

Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used for many years inCanada and recently in Australia to boost octane. It also helps old cars designed for leadedfuel run on unleaded fuel without need for additives to prevent valve problems.

US Federal sources state that MMT is suspected to be a powerful neurotoxin and respiratorytoxin,[19] and a large Canadian study concluded that MMT impairs the effectiveness of automobile emission controls and increases pollution from motor vehicles.[20]

In 1977 use of MMT was banned in the US by the Clean Air Act until the Ethyl Corporationcould prove that the additive would not lead to failure of new car emission-control systems.As a result of this ruling, the Ethyl Corporation began a legal battle with the EPA, presentingevidence that MMT was harmless to automobile emissions-control systems. In 1995 the US

Court of Appeals ruled that the EPA had exceeded its authority, and MMT became a legalfuel additive in the US. MMT is nowadays manufactured by the Afton Chemical Corporationdivision of Newmarket Corporation.[21]

[edit] Ethanol

[edit] United States

In the United States, ethanol is sometimes added to gasoline but sold without an indicationthat it is a component.

In several states, ethanol is added by law to a minimum level which is currently 5.9%. Mostfuel pumps display a sticker stating that the fuel may contain up to 10% ethanol, an

intentional disparity which allows the minimum level to be raised over time without requiringmodification of the literature/labelling. The bill[citation needed ] which was being debated at thetime the disclosure of the presence of ethanol in the fuel was mandated has recently passed.

[edit] European Union

In the EU, 5% ethanol can be added within the common gasoline spec (EN 228). Discussionsare ongoing to allow 10% blending of ethanol. Most gasoline sold in Sweden has 5-15%ethanol added, also there is sold petrol blended ethanol, 85% ethanol 15% petrol.

[edit] Brazil

In Brazil, the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP)requires that gasoline for automobile use has 25% of ethanol added to its composition.

[edit] Australia

Legislation limits ethanol use to 10 per cent of gasoline in Australia. It is commonly calledE10 by major brands and is less expensive than regular unleaded petrol. It is also required for retailers to label fuels containing ethanol on the dispenser.

[edit] Dye

Main article: Fuel dyes

In the United States the most commonly used aircraft gasoline, avgas, or aviation gas, isknown as 100LL (100 octane, low lead) and is dyed blue. Red dye has been used for identifying untaxed (non-highway use) agricultural diesel.

The UK uses red dye to differentiate between regular diesel fuel, (often referred to as DERVfrom Diesel-Engined Road Vehicle), which is undyed, and diesel intended for agricultural and

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construction vehicles like excavators and bulldozers. Red diesel is still occasionally used onHGVs which use a separate engine to power a loader crane. This is a declining practicehowever, as many loader cranes are powered directly by the tractor unit.

In India, where leaded fuels are mainstream, petrol is dyed red.

[edit] Oxygenate blendingOxygenate blending adds oxygen to the fuel in oxygen-bearing compounds such as MTBE, ETBE and ethanol, and so reduces the amount of carbon monoxide and unburned fuel in theexhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending ismandated by EPA regulations to reduce smog and other airborne pollutants. For example, inSouthern California, fuel must contain 2% oxygen by weight, resulting in a mixture of 5.6%ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline. The federal requirement that RFG contain oxygen was dropped 6 May2006 because the industry had developed VOC-controlled RFG that did not need additionaloxygen.[22]

MTBE use is being phased out in some states due to issues with contamination of ground

water. In some places, such as California, it is already banned. Ethanol and to a lesser extentthe ethanol derived ETBE are common replacements. Since most ethanol is derived from

 biomatter such as corn, sugar cane or grain, it is referred to as bio-ethanol. A commonethanol-gasoline mix of 10% ethanol mixed with gasoline is called gasohol or E10, and anethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85. The most extensiveuse of ethanol takes place in Brazil, where the ethanol is derived from sugarcane. In 2004,over 3.4 billion US gallons (2.8 billion imp gal/13 million m³) of ethanol was produced in theUnited States for fuel use, mostly from corn, and E85 is slowly becoming available in muchof the United States, though many of the relatively few stations vending E85 are not open tothe general public.[23] The use of  bioethanol, either directly or indirectly by conversion of such ethanol to bio-ETBE, is encouraged by the European Union Directive on the Promotion

of the use of biofuels and other renewable fuels for transport. However since producing bio-ethanol from fermented sugars and starches involves distillation, ordinary people in much of Europe cannot legally ferment and distill their own bio-ethanol at present (unlike in the USwhere getting a BATF distillation permit has been easy since the 1973 oil crisis.)

[edit] Other additives

Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates.

[edit] Health concerns

Uncontrolled burning of gasoline produces large quantities of  soot.

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Many of the non-aliphatic hydrocarbons naturally present in gasoline (especially aromaticones like benzene), as well as many anti-knocking additives, are carcinogenic. Because of this, any large-scale or ongoing leaks of gasoline pose a threat to the public's health and theenvironment, should the gasoline reach a public supply of  drinking water . The chief risks of such leaks come not from vehicles, but from gasoline delivery truck accidents and leaks from

storage tanks. Because of this risk, most (underground) storage tanks now have extensivemeasures in place to detect and prevent any such leaks, such as sacrificial anodes. Gasoline israther volatile (meaning it readily evaporates), requiring that storage tanks on land and invehicles be properly sealed. The high volatility also means that it will easily ignite in hotweather conditions, unlike diesel for example. Appropriate venting is needed to ensure thelevel of pressure is similar on the inside and outside. Gasoline also reacts dangerously withcertain common chemicals.

Gasoline is also one of the sources of pollutant gases. Even gasoline which does not containlead or sulfur  compounds produces carbon dioxide, nitrogen oxides, and carbon monoxide inthe exhaust of the engine which is running on it. Furthermore, unburnt gasoline andevaporation from the tank , when in the atmosphere, react in sunlight to produce

 photochemical smog. Addition of ethanol increases the volatility of gasoline.Through misuse as an inhalant, gasoline also contributes to damage to health. Concentrationsof gasoline as low as 0.25 ppm[citation needed ] (0.000 025%) can be smelt by most people. Petrolsniffing is a common way of obtaining a high for many people and has become epidemic insome poorer communities and indigenous groups in America, Australia, Canada, NewZealand and some Pacific Islands.[24] In response, Opal fuel has been developed by the BP Kwinana Refinery in Australia, and contains only 5% aromatics (unlike the usual 25%) whichinhibits the effects of inhalation.[25]

Like other alkanes, gasoline burns in a limited range of its vapor phase and, coupled with itsvolatility, this makes leaks highly dangerous when sources of ignition are present. Gasoline

has a lower explosion limit of 1.4% by volume and an upper explosion limit of 7.6%. If theconcentration is below 1.4% the air-gasoline mixture is too lean and will not ignite. if theconcentration is above 7.6% the mixture is too rich and also will not ignite. However,gasoline vapor rapidly mixes and spreads with air making unconstrained gasoline quicklyflammable. Many accidents involve gasoline being used in an attempt to light bonfires; rather than helping the material on the bonfire to burn, some of the gasoline vaporises quickly after 

 being poured and mixes with the surrounding air, so when the fire is lit a moment later thevapor surrounding the bonfire instantly ignites in a large fireball, engulfing the unwary user.The vapor is also heavier than air and tends to collect in garage inspection pits.

[edit] Usage and pricing

Main articles: Gasoline usage and pricing, Global warming, and Peak oil

2009 EU, Romanian gas station.

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UK petrol prices.

The US accounts for about 44% of the world’s gasoline consumption.[26] In 2003 The USconsumed 476.474 gigalitres (1.25871×1011 US gal; 1.04810×1011 imp gal),[27] which equatesto 1.3 gigalitres of gasoline each day (about 360 million US or 300 million imperial gallons).The US used about 510 billion litres (138 billion US gal/115 billion imp gal) of gasoline in2006, of which 5.6% was mid-grade and 9.5% was premium grade.[28]

Western countries have among the highest usage rates per person.[citation needed ]

Based on externalities, some countries, e.g. in Europe and Japan, impose heavy fuel taxes onfuels such as gasoline.[citation needed ]

[edit] United States

Because a greater proportion of the price of gasoline in the United States is due to the cost of oil, rather than taxes, the price of the retail product is subject to greater fluctuations (vs.outside the US) when calculated as a percentage of cost-per-unit, but is less variable inabsolute terms. From 1998 to 2004 the price of gasoline was between $1 to $2 USD  per  U.S.gallon.[29] After 2004, the price increased until the average gas price reached a high of $4.11

 per U.S. gallon in mid-2008, but has receded to approximately $2.60 per U.S. gallon as of September 2009.[29]

Unlike other goods[which?] in the United States, gasoline is sold with tax included. Taxes areadded by federal, state and local governments. As of 2009, the federal tax is 18.4¢ per gallonfor gasoline and 24.4¢ per gallon for diesel (excluding Red diesel).[30] Among states, thehighest gasoline tax rates, including the federal taxes as of 2005, are New York (62.9¢/gal),Hawaii (60.1¢/gal), & California (60¢/gal).[31] However, many states' taxes are a percentageand thus vary in amount depending on the cost of the gasoline.

About 9 percent of all gasoline sold in the US in May 2009 was premium gas, according tothe Energy Information Administration. Consumer Reports magazine says “If your car canrun on regular, run it on regular.”[citation needed ] The Associated Press said that premium gas— 

which is a higher octane and costs several cents a gallon more than regular unleaded-should be used only if the manufacturer says it is “required.” [32]

[edit] StabilityGood quality gasoline should be stable almost indefinitely if stored properly. Such storageshould be in an airtight container, to prevent oxidation or water vapors mixing, and at a stablecool temperature, to reduce the chance of the container leaking. When gasoline is not storedcorrectly and is left for a period of time, gums and varnishes may build up and precipitate inthe gasoline, causing "stale fuel". This may cause gums to build up in the fuel tank, lines, andcarburetor or fuel injection components making it harder to start the engine. However uponthe resumption of regular vehicle usage, the buildups should eventually be cleaned up by the

flow of fresh petrol. A fuel stabilizer may be used to extend the life of the fuel that is not or cannot be stored properly. Fuel stabilizer is commonly used for small engines such as

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lawnmower and tractor engines to promote quicker and more reliable starting. Users have been advised to keep gasoline containers and tanks more than half full and properly capped toreduce air exposure, to avoid storage at high temperatures,[33] to run an engine for ten minutesto circulate the stabilizer through all components prior to storage, and to run the engine atintervals to purge stale fuel from the carburetor .[34]

Gummy, sticky resin deposits result from oxidative degradation of gasoline. This degradationcan be prevented through the use of antioxidants such as phenylenediamines,alkylenediamines (diethylenetriamine, triethylenetetramine, etc.), and alkylamines (diethylamine, tributylamine, ethylamine). Other useful additives include gum inhibitors suchas N-substituted alkylaminophenols and colour stabilizers such as N-(2-aminoethyl)piperazine, N,N-diethylhydroxylamine, and triethylenetetramine.[35]

Improvements in refinery techniques have generally reduced the reliance on the catalyticallyor thermally cracked stocks most susceptible to oxidation.[36] Gasoline containing acidiccontaminants such as naphthenic acids can be addressed with additives including strongly

 basic organo-amines such as N,N-diethylhydroxylamine, preventing metal corrosion and breakdown of other antioxidant additives due to acidity. Hydrocarbons with a brominenumber of 10 or above can be protected with the combination of unhindered or partiallyhindered phenols and oil soluble strong amine bases such as monoethanolamine, N-(2-aminoethyl)piperazine, cyclohexylamine, 1,3-cyclohexane-bis(methylamine), 2,5-dimethylaniline, 2,6-dimethylaniline, diethylenetriamine and triethylenetetramine.[35]

"Stale" gasoline can be detected by a colorimetric enzymatic test for organic peroxides produced by oxidation of the gasoline.[37]